Method for producing copper and apparatus for producing copper

ABSTRACT

A method for producing copper includes a first step of dissolving copper by adding a copper-containing material to a solution containing an oxidant, and a second step of depositing copper on a surface of a cathode by bringing a solution (A) containing the oxidant in a reduced state into contact with a solution (B) containing copper dissolved therein with a separator provided between the solution (A) and the solution (B), arranging an anode in the solution (A), arranging the cathode in the solution (B), and applying a voltage to both the electrodes, while the oxidant contained in the solution (A) is regenerated, in which the oxidant has a standard electrode potential of 1.6 V or less.

TECHNICAL FIELD

The present invention relates to a method for producing copper by electrolytic refining and an apparatus for producing copper.

BACKGROUND ART

In general, copper and copper alloys are metals that are in high demand like iron, aluminum, and so forth. It is thus important to collect, for example, discarded electric wires and printed circuit boards in home appliances and recover copper from copper scraps that contain copper from the viewpoint of protecting resources.

However, low-purity copper is often discarded without being reused in the present circumstances for economic reasons. Furthermore, in the recycling of copper from electric wires, there has been copper that cannot be recovered. Although in some cases copper is recycled in large-scale smelters, a certain amount of waste is required for recycling, and transportation costs are high.

For example, when copper is recovered from copper scraps collected from markets, in the case of power cables, copper is recovered by stripping sheath resins that cover copper wires to separate copper wires from resins. For communication cables, in the case of thick cables, copper can also be separated and recovered by stripping sheath resins, whereas in the case of thin cables, workloads are excessively heavy; thus, such a recovery method cannot be performed.

In the case of thin communication cables, cables are pulverized while copper wires are covered with resins, and then gravity separation is performed. However, small amounts of resins are left on the surface of copper; thus, resins need to be burned away by firing.

Although the recovery of copper by a dry process as described above is a simple process, carbon dioxide is generated by the combustion of resins to lead to high environmental loads. Furthermore, copper is recovered in the form of copper oxide; thus, reduction treatment needs to be performed. Moreover, metallic copper recovered has a low purity, depending on the purity of raw-material copper scraps collected from markets.

In the case where copper is recovered from printed-circuit boards used in, for example, personal computers and home appliances, a recovery method using a wet process is known in addition to a dry process. The wet process is a process for recovering copper by leaching copper with, for example, sulfuric acid or hydrochloric acid and performing electrolytic refining.

However, oxygen is generated on an anode in the wet process; thus, the wet process has a disadvantage that power consumption during electrolysis is inevitably increased.

There is a method for recovering copper by a cementation method with an etching solution. In this case, iron chloride or copper chloride is generally used for the etching solution, and regeneration is performed not by electrolysis but with chlorine gas. Thus, the use of chlorine gas requires specialized management techniques.

For example, PTL 1 discloses a method for recovering metallic copper by arranging a cathode to deposit metallic copper in a monovalent copper ion-containing solution, an anode in an ammonia-alkaline solution containing a monovalent copper ion, and a separator between the cathode and the anode, and passing a current through the electrodes to perform electrolysis while the solution is transferred from the cathode side to the anode side. According to the method described in PTL 1, metallic copper is deposited on a cathode portion. Simultaneously, monovalent copper ions can be converted into divalent copper ions in an anode portion. Furthermore, a divalent copper ion solution is taken and introduced into a dissolution layer containing metallic copper waste and a complex compound. A monovalent copper ion-containing solution obtained by treating the metallic copper waste is used as the foregoing monovalent copper ion-containing solution. This results in lower power consumption than ever before.

However, a target solution to be treated for the recovery of copper contains various ions of metals such as manganese, nickel, zinc, and lead; thus, such metallic ions need to be removed before electrolysis operation. Furthermore, ammonia is used in the method described in PTL 1; thus, if the metallic copper waste contains a resin, the resin can react with ammonia. If the resin reacts with ammonia, ammonia is undesirably consumed. In addition, there is a problem that impurities in the resin are easily dissolved in the ammonia-alkaline solution.

In the foregoing circumstances, the inventors have previously developed a method for producing a metal such as copper by electrolytic refining (see PTL 2).

CITATION LIST Patent Literature

PTL 1: Japanese Unexamined Patent Application Publication No. 2003-253484

PTL 2: Japanese Unexamined Patent Application Publication No. 2014-040639

SUMMARY OF INVENTION Technical Problem

A method described in PTL 2 is a method for producing a metal by partitioning an electrolytic layer into a cathode chamber and an anode chamber with a cation-exchange membrane and performing the electrolysis with a solution containing a metal dissolved therein using an oxidant and a solution containing the oxidant in a reduced state to deposit a metal on a surface of a cathode. According to this method, the oxidant can be regenerated in the anode chamber including a diamond electrode while the metal is recovered in the cathode chamber. Thus, chemical agents are not consumed in principle. Accordingly, although the initial cost is high because of the use of the diamond electrode, the main operating cost is only the electricity cost required for electrolysis.

However, the inventors have further conducted studies and have found that because an oxidant, such as ammonium persulfate or hydrogen peroxide, which has a high oxidative power, is used in the method described in PTL 2, a reaction with water occurs to cause self-discharge. This phenomenon is noticeable when the solution is allowed to stand. The solution that remains unused for a certain period can be degraded.

Furthermore, a certain amount of the oxidant is not effectively used for the dissolution of the metal. There is a room for improvement from the viewpoint of refining the metal at low cost.

It is an object of the present invention to provide a method for efficiently producing high-purity copper at low cost by a wet process without increasing the environmental load or producing a waste liquid.

Solution to Problem

A method for producing copper according to an aspect of the present invention includes:

(1) a first step of dissolving copper by adding a copper-containing material to a solution containing an oxidant; and

a second step of depositing copper on a surface of a cathode by bringing a solution (A) containing the oxidant in a reduced state into contact with a solution (B) containing copper dissolved therein with a separator provided between the solution (A) and the solution (B), arranging an anode in the solution (A), arranging the cathode in the solution (B), and applying a voltage to both the electrodes, while the oxidant contained in the solution (A) is regenerated,

in which the oxidant has a standard electrode potential of 1.6 V or less.

Advantageous Effects of Invention

According to the present invention, it is possible to provide the method for efficiently producing high-purity copper at low cost by a wet process without increasing the environmental load or producing a waste liquid.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates the outline of a method for producing copper according to an embodiment of the present invention.

FIG. 2 illustrates the outline of a method for producing copper according to an embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS Description of Embodiments of Invention

Embodiments of the present invention are first listed and explained.

(1) A method for producing copper according to an embodiment of the present invention includes:

a first step of dissolving copper by adding a copper-containing material to a solution containing an oxidant; and

a second step of depositing copper on a surface of a cathode by bringing a solution (A) containing the oxidant in a reduced state into contact with a solution (B) containing copper dissolved therein with a separator provided between the solution (A) and the solution (B), arranging an anode in the solution (A), arranging the cathode in the solution (B), and applying a voltage to both the electrodes, while the oxidant contained in the solution (A) is regenerated,

in which the oxidant has a standard electrode potential of 1.6 V or less.

According to the invention described in item (1), it is possible to provide the method for efficiently producing high-purity copper at low cost by a wet process without increasing the environmental load or producing a waste liquid.

(2) In the method for producing copper described in item (1), the oxidant is preferably one or more selected from the group consisting of iron ions, manganese ions, vanadium ions, and chromium ions.

According to the invention described in item (2), self-discharge does not occur in the solution containing the oxidant, thus enabling copper to be efficiently dissolved.

(3) In the method for producing copper described in item (1) or (2),

preferably, after the second step of depositing copper, the solution (A) in which the anode is arranged is recovered, and the solution (A) is reused as the solution containing the oxidant in the first step.

According to the invention described in item (3), when the first step and the second step are repeated, the solution (A) containing the regenerated oxidant is reused as a “solution containing an oxidant”, thereby reducing the cost required for the production of copper.

(4) In the method for producing copper described in one of items (1) to (3),

preferably, after the second step of depositing copper, the solution (B) in which the cathode is arranged is recovered, and the solution (B) is reused as the solution (A) in the second step.

According to the invention described in item (4), when the first step and the second step are repeated, the solution (B) from which copper has been removed by deposition is reused as the solution (A) in which the anode is arranged, thereby reducing the cost required for the production of copper.

(5) In the method for producing copper described in one of items (1) to (4),

preferably, in the first step of dissolving copper, the copper-containing material is excessively added in such a manner that all the oxidant is in a reduced state.

According to the invention described in item (5), undesired power consumption is inhibited, thus enabling copper to be produced at low cost.

(6) In the method for producing copper described in one of items (1) to (5),

preferably, in the second step of depositing copper, the solution (B) containing copper dissolved therein has a copper concentration of 12 g/L or more.

According to the invention described in item (6), when the method for producing copper is continuously performed, the method can be performed while maintaining a good state in which electrodeposition of copper can be stably performed.

(7) An apparatus for producing copper according to an embodiment of the present invention is used in the method for producing copper described in one of items (1) to (6) and includes:

a reservoir tank for a solution containing an oxidant, at least one dissolution tank, a reservoir tank for a solution containing copper dissolved therein, an electrolytic bath, and a reservoir tank for a solution containing the oxidant in a reduced state,

in which the electrolytic bath is partitioned with a separator into an oxidant regeneration chamber including an anode and a plating chamber including a cathode.

According to the invention described in item (7), it is possible to provide the apparatus for producing copper, the apparatus enabling the method for producing copper described in one of items (1) to (7) to be efficiently and continuously performed.

(8) In the apparatus for producing copper described in item (7), the at least one dissolution tank preferably comprises a plurality of dissolution tanks.

According to the invention described in item (8), copper dissolution that requires a longer time than that taken to perform the second step of depositing copper can be performed in the dissolution tanks in parallel. Thus, copper is dissolved to enable the oxidant to react completely while the second step of depositing copper is performed; hence, an efficient operation can be performed.

Details of Embodiments of the Invention

Specific examples of a method for producing copper and an apparatus for producing copper according to embodiments of the present invention will be described in more detail below. The present invention is not limited to these examples and is indicated by the appended claims. It is intended to include any modifications within the scope and meaning equivalent to the scope of the claims.

Method for Producing Copper (First Step of Dissolving Copper)

A first step of dissolving copper is a step in which a solution containing an oxidant is used and a copper-containing material is added to the solution to dissolve copper.

In this step, copper (Cu) is dissolved in the solution to form copper ions (Cu²⁺), and the oxidant in the solution is in a reduced state. For example, when the oxidant is composed of iron ions (Fe³⁺), the oxidant is reduced into Fe²⁺. At this time, preferably, the oxidant in the solution is completely consumed for the dissolution of copper. That is, in the first step of dissolving copper, preferably, the copper-containing material is excessively added in such a manner that all the oxidant is in a reduced state. This can suppress power consumption due to the reduction of the remaining oxidant in the subsequent second step of depositing copper. Thus, an electrodeposition efficiency close to 100% can be achieved, enabling the production of copper at lower cost.

—Copper-Containing Material—

The copper-containing material may be any material containing copper. The use of items, such as waste, collected from markets can contribute to resource conservation. For example, copper wires, printed-circuit boards of personal computers and home appliances, semiconductors, electronic devices, motors, automobile shredder fluff, and harness connectors can be used.

Because the copper-containing material is added to the solution containing the oxidant and dissolved, the copper-containing material is preferably pulverized as finely as possible, so that the surface area is increased to reduce the dissolution time. Although a powder form is preferred, any other form may be used. Specifically, the copper-containing material is preferably pulverized so as to have a size of about 3 mm or less.

To prevent the contamination of a tank with pulverized materials that are not dissolved in the solution and that spread in the solution, the pulverized copper-containing material is preferably packed into, for example, a filter or a filter cloth (such as a pouch composed of, for example, a resin or fibers) before use. After copper is dissolved in the solution, insoluble matter may be removed by filtering the solution.

When the pulverized insoluble matter that is not dissolved in the solution is heavy, the insoluble matter may be recovered by placing, for example, a tray on the bottom of a tank such as a dissolution tank and removing sediments.

The copper-containing material is preferably a powder mixture of copper and material substantially insoluble in the solution containing the oxidant.

For example, when the copper-containing material is a powder mixture of copper and a resin, the resin is not dissolved in the solution containing the oxidant and thus can be removed from the solution by, for example, filtration. When the copper-containing material contains a component soluble in the solution containing the oxidant, the component is accumulated as an impurity in the solution and can be mixed as an impurity with copper in the second step of depositing copper as described below. However, copper is a metal having a high redox potential and thus can be recovered in a state of being substantially free from an impurity in the second step of depositing copper as described below. That is, only copper can be recovered in a state in which a potential at which copper is deposited is applied while the impurity remains dissolved.

When the oxidant is composed of iron ions, a solution containing Fe³⁺ dissolves most of metals other than noble metals. Thus, for example, when a powder mixture of copper and a noble metal is used, the noble metal and so forth insoluble in the solution containing Fe³⁺ are recovered by, for example, filtration, and then copper can be recovered in the second step of depositing copper as described below.

Specific examples of a component mixed with copper include resins, gold, platinum, silver, tungsten, molybdenum, titanium, and ceramics. Examples of such a copper-containing material include plating sludge and grinding sludge. Resins, gold, platinum, silver, tungsten, molybdenum, titanium, and ceramics are components that are completely insoluble in the solution containing the oxidant or that are substantially unnecessary to the extent that very small amounts thereof are slowly dissolved.

—Oxidant—

The oxidant may be an oxidant that can dissolve copper and has a standard electrode potential of 1.6 V or less. A standard electrode potential of the oxidant of 1.6 V or less can result in the inhibition of the degradation of the solution due to self-discharge. The oxidant preferably has a standard electrode potential of 1.5 V or less, more preferably 1.4 V or less.

Examples of the oxidant include iron ions, manganese ions, vanadium ions, and chromium ions. These oxidants may be used separately or in combination as a mixture of different types thereof. Depending on the type of oxidant, when a single type of oxidant is used, whether copper is sufficiently dissolved or not can be easily determined by a change in the color of the solution.

Among the foregoing oxidants, iron ions are optimally used from the viewpoint of resource potential, reusability, safety, its ability to dissolve copper, low electrolysis voltage, ease of valence control, and the distinguishability of the change in color.

—Solution Containing Oxidant—

The solution containing the oxidant may be any solution containing the oxidant. When the oxidant is composed of iron ions, for example, a ferric sulfate solution or a ferric chloride solution can be preferably used.

When the oxidant is composed of manganese ions, for example, manganese sulfate can be preferably used. When the oxidant is composed of vanadium ions, for example, vanadium sulfate can be preferably used. When the oxidant is composed of chromium ions, for example, chromium sulfate can be preferably used.

In the solution containing the oxidant, the oxidant concentration may be appropriately changed, depending on the type of oxidant. For example, when the ferric sulfate solution is used as the solution containing the oxidant, the concentration of iron ions is preferably 10 g/L or more and 130 g/L or less, more preferably 15 g/L or more and 110 g/L or less, even more preferably 20 g/L or more and 90 g/L or less. A concentration of iron ions in the ferric sulfate solution of 10 g/L or more enables a certain amount of copper in the copper-containing material to be dissolved in the solution, so that a sufficient amount of copper can be produced in one operation. A concentration of iron ions of 130 g/L or less can result in a reduction in the risk of depositing salts of iron and copper.

When the ferric sulfate solution is used as the solution containing the oxidant, a high pH can be liable to cause the precipitation of iron hydroxide and can lead to a low stability of the solution to increase the copper concentration. From this point of view, the ferric sulfate solution preferably has a pH of 4 or less, more preferably 3.5 or less, even more preferably 3 or less.

(Second Step of Depositing Copper)

The second step of depositing copper will be described in detail with reference to FIG. 1. FIG. 1 schematically illustrates how solutions change before and after the second step of depositing copper.

In the second step of depositing copper, a solution (A) 6 containing an oxidant in a reduced state and a solution (B) 5 containing copper dissolved therein are brought into contact with each other with a separator 4 provided therebetween. For example, a separator may be arranged to divide a normal electrolytic bath into two chambers, the solution (A) 6 containing the oxidant in a reduced state may be placed in one of the chambers, and the solution (B) 5 containing copper dissolved therein may be placed in the other chamber.

An anode 2 is arranged in the solution (A) 6 containing the oxidant in a reduced state. A cathode 1 is arranged in the solution (B) 5 containing copper dissolved therein. Both the electrodes are connected to a rectifier 3. A voltage is applied thereto to pass a current, thereby performing electrolytic refining.

Although the second step of depositing copper will be described below by illustrating the case of using iron ions as the oxidant, even when another oxidant is used, it can be performed on a similar principle.

When iron ions are used as the oxidant, Cu²⁺ and Fe²⁺ are present in the solution (B) 5 containing copper dissolved therein. Electrolysis is performed to deposit metallic copper on a surface of the cathode 1. Although Fe²⁺ is present in the solution (A) 6 containing the oxidant in a reduced state, Fe²⁺ is oxidized into Fe³⁺ by electrolysis.

By performing the second step of depositing copper, the solution (B) 5 containing copper dissolved therein is converted into a solution 7 from which copper has been removed by deposition, and the solution (A) 6 containing the oxidant in a reduced state is converted into a solution 8 containing the regenerated oxidant.

When the method for producing copper according to an embodiment of the present invention is repeatedly performed, preferably, after the second step of depositing copper, the solution (A) in which the anode is arranged is recovered, and then the solution (A) is reused as the solution containing the oxidant in the first step.

In an example in which when iron ions are used as the oxidant, the solution in which the anode 2 is arranged is the solution 8 containing the regenerated oxidant. A large amount of Fe³⁺ is present in this solution. Thus, when the method for producing copper according to an embodiment of the present invention is performed repeatedly and continuously, the solution can be used as the solution containing the oxidant.

Furthermore, when the method for producing copper according to an embodiment of the present invention is repeatedly performed, after the second step of depositing copper, the solution (B) in which the cathode is arranged is recovered, and then the solution (B) is preferably reused as the solution (A) in the second step.

In an example in which when iron ions are used as the oxidant, the solution in which the cathode 1 is arranged is the solution 7 from which copper has been removed by deposition. A large amount of Fe²⁺ is present in this solution. Thus, when the method for producing copper according to an embodiment of the present invention is performed repeatedly and continuously, the solution can be used as the solution (A) 6 containing the oxidant in a reduced state.

Moreover, when the method for producing copper according to an embodiment of the present invention is repeatedly performed, in the second step of depositing copper on a surface of the cathode, the solution (B) containing copper dissolved therein preferably has a copper concentration of 12 g/L or more. This maintains a good state in which copper is stably subjected to electrodeposition, thereby enabling copper to be produced repeatedly and continuously. Preferably, a copper concentration of 12 g/L or more is always ensured in the second step. When copper concentration is less than 12 g/L, the application of a voltage is preferably stopped. The copper concentration in the second step is more preferably 15 g/L or more, more preferably 18 g/L or more.

When the method for producing copper according to an embodiment of the present invention is repeatedly performed, for example, a movable electrolytic bath is used, and the anode and the cathode are interchanged. Specifically, after the second step of depositing copper, the copper-containing material is added to the solution containing the regenerated oxidant to dissolve copper, the anode and the cathode are interchanged, and then electrolysis may be performed. The first step and the second step can also be repeated by interchanging the solutions with, for example, pumps. Furthermore, by using a plurality of dissolution tanks in the first step of dissolving copper, an efficient method can be performed in which electrolysis is performed while the steps of dissolving copper and filtering insoluble matter, which require time, proceeds. In this case, preferably, tanks that control the solutions are provided, and the solutions can be circulated by transferring the solutions to the tanks with, for example, pumps.

In the second step of depositing copper, the solutions are preferably stirred because of, for example, a good deposition state of copper. The stirring may be performed by a common method such as air bubbling or the circulation of the solutions with, for example, pumps.

As an alternative method, the solutions may be circulated through the electrolytic bath like a redox-flow cell. A plurality of electrolytic baths may be connected together in series or parallel.

When the solutions are not stirred on purpose, copper can be deposited in the form of powder.

To stabilize the state of electrodeposition of copper, for example, an additive may be added to the solution (B) containing copper dissolved therein. As the additive, an additive commonly used in techniques of copper plating and electrolytic refining of copper can be used. In order not to co-deposit impurities, appropriate additives such as materials that form complexes with impurities may be added thereto. A material that precipitates impurities or on which impurities adsorb may be added to the solution (B) to prevent co-deposition.

In the case where the method for producing copper according to an embodiment of the present invention is repeatedly performed and where the solution (A) containing oxidant in a reduced state and the solution (B) containing copper dissolved therein are continued to be reused, impurities can be accumulated in the solutions. In this case, impurities may be precipitated by, for example, pH adjustment, and removed. A process in which impurities are electrodeposited by electrolysis under severer conditions than normal conditions, i.e., what is called dummy plating, may be performed. When the copper concentration is excessively increased, the copper concentration can be adjusted in the same way as above. In this case, an iron-free solution such as sulfuric acid may be used on the counter-electrode side.

If the solution (B) containing copper dissolved therein and the solution (A) containing the oxidant in a reduced state contain a large amount of chlorine, chlorine gas can be generated during electrolysis; thus, the solutions are preferably free from chlorine. In the case where a trace amount of chlorine is contained in the solutions, there is no problem. The solution (A) and the solution (B) mainly containing sulfuric acid are preferred because of their easy handling.

The temperature of the solution (A) and the solution (B) may be room temperature or a high temperature such as 60° C. during electrolysis. The use of an excessively low solution temperature may facilitate the deposition of a salt, whereas the use of an excessively high solution temperature may cause the instability of the state of electrodeposition and may result in the evaporation of water to make it difficult to control the solutions. From this point of view, the temperature of the solution (A) and the solution (B) is preferably 10° C. or higher and 70° C. or lower, more preferably 15° C. or higher and 65° C. or lower, even more preferably 20° C. or higher and 60° C. or lower during electrolysis.

—Cathode—

As the cathode, any electrode can be used as long as copper can be deposited on a surface of the electrode. For example, copper, platinum, gold, titanium, or stainless steel can be used. From the viewpoint of depositing copper, copper foil is preferably used as a seed material. For example, a stainless steel plate or titanium plate may be used as a blank to peel and recover electrodeposited copper.

—Anode—

As the anode, an electrode that can maintain a stable state during electrolysis may be used. For example, carbon, lead, a noble metal, titanium, or tungsten can be used. A titanium lath coated with a noble metal may also be used.

—Separator—

Although the separator is preferably a membrane capable of transmitting only hydrogen ions because the maximum electrolysis efficiency is obtained, a membrane that transmits other ions can also be used. In the case of an ion-exchange membrane, cation-exchange membrane or anion-exchange membrane may be used. An unglazed plate or a filter cloth can also be used.

Apparatus for Producing Copper

An example of an apparatus for producing copper according to an embodiment of the present invention will be described in detail with reference to FIG. 2.

The apparatus for producing copper according to an embodiment of the present invention is an apparatus with which the method for producing copper according to an embodiment of the present invention can be performed and includes a reservoir tank 21 for a solution containing an oxidant, a dissolution tank 22, a reservoir tank 23 for a solution containing copper dissolved therein, an electrolytic bath 24, and a reservoir tank 25 for a solution containing the oxidant in a reduced state. The electrolytic bath 24 is partitioned with a separator 244 into a plating chamber including a cathode and an oxidant regeneration chamber including an anode.

Arrows in FIG. 2 indicate the flows of the solutions. The solutions may be circulated with, for example, pumps.

For example, the method for producing copper according to an embodiment of the present invention with the apparatus for producing copper according to an embodiment of the present invention may be performed as described below.

A solution containing an oxidant is prepared and supplied to the dissolution tank 22. A copper-containing material 221 is added thereto to dissolve copper with stirring or the like. For example, when the solution is stirred with a propeller, the dissolution tank 22 is preferably a circular tank in plan view. Insoluble matter is removed from the resulting solution containing copper, as needed. The solution is transferred to the reservoir tank 23 for a solution containing copper dissolved therein. The dissolution of copper and the filtration of the solution can require time, compared with the electrolytic refining of copper. To achieve the reduced state of all the oxidant, a sufficient amount of time is preferably ensured. Thus, a plurality of dissolution tanks 22 are preferably provided. In this case, copper can be dissolved to allow the oxidant to react completely during the second step of depositing copper, thereby efficiently producing copper without loss of time. When the step of dissolving copper and the step of depositing copper are simultaneously performed, it is possible to avoid a state in which the step of depositing copper is first completed to hold the solution in the electrolytic bath 24.

The solution containing copper dissolved therein is transferred to the plating chamber of the electrolytic bath 24. A solution containing an oxidant in a reduced state, the solution being prepared in the reservoir tank for a solution containing an oxidant in a reduced state is supplied to the oxidant regeneration chamber of the electrolytic bath 24. A voltage is applied to both the solutions to pass a current, thus performing electrolysis. Thereby, high-purity metallic copper can be deposited on a surface of a cathode 241.

After the electrolysis is completed, copper is removed by deposition from the solution in the plating chamber to provide a solution containing the oxidant in a reduced state. The resulting solution is removed with a pump and transferred to the reservoir tank 25 for a solution containing the oxidant in a reduced state. The solution in the oxidant regeneration chamber is in a state in which the oxidant is oxidized and is in a regenerated state; thus, the solution is transferred to the reservoir tank 21 for a solution containing an oxidant.

As described above, by operating the apparatus for producing copper according to an embodiment of the present invention the method for producing copper according to an embodiment of the present invention can be performed repeatedly and continuously.

In the apparatus for producing copper according to an embodiment of the present invention, the components such as the cathode can have the same structure as those described in the method for producing copper according to an embodiment of the present invention.

EXAMPLES

While the present invention will be described in more detail below by examples, these examples are illustrative, and a method for producing copper and an apparatus for producing copper according to the present invention are not limited to these examples. The scope of the invention is defined by the following claims, and is intended to include any modifications within the scope and meaning equivalent to the scope of the claims.

Example 1 (First Step of Dissolving Copper)

As a copper-containing material, 3000 g of pulverized scrap electric wires containing, by mass, about 50% copper and about 50% resin were prepared. The pulverized scrap electric wires were in the form of powder having a size of about 1 mm.

As a solution containing an oxidant, 80 L of a ferric sulfate solution having an iron ion concentration of 30 g/L was prepared. Copper sulfate was added to the ferric sulfate solution to adjust the copper ion concentration to 20 g/L.

The ferric sulfate solution and the pulverized scrap electric wires were placed into the dissolution tank. The mixture was stirred for 6 hours to dissolve copper, thereby preparing a solution containing copper dissolved therein. The solution containing copper dissolved therein had a copper ion concentration of 40 g/L. The residual resin was removed by filtering the solution.

(Second Step of Depositing Copper)

An electrolytic bath was partitioned with a Nafion 117, which is a cation-exchange membrane, serving as a separator. The solution containing copper dissolved therein was placed into one chamber. Into the other chamber, 80 L of ferrous sulfate containing iron ions that had been reduced into Fe²⁺ was placed as a solution (A) containing the oxidant in a reduced state. The ferrous sulfate had an iron ion concentration of 30 g/L. Copper sulfate was added to the solution (A) to adjust the copper ion concentration to 20 g/L.

Copper foil serving as a cathode was arranged in a plating chamber in which the solution containing copper dissolved therein was placed. A titanium lath coated with platinum, which served as an anode, was arranged in an oxidant regeneration chamber in which the solution (A) containing the oxidant in a reduced state was placed.

A rectifier was connected to both the electrodes. A voltage was applied to perform electrolysis. In this case, the voltage was 3.8 V. The temperature of the solutions was

The electrolysis was performed for 15 hours to deposit 1500 g of copper on the cathode. The copper had a purity of 99.9% or more. The electrodeposition efficiency was 99%.

The foregoing steps were repeated 10 cycles to obtain a total of 15 kg of copper.

When the steps were repeated, after the second step of depositing copper, the solution (A) in which the anode was arranged was reused as the solution containing the oxidant, and the solution (B) in which the cathode was arranged was reused as the solution (A) containing the oxidant in a reduced state. In the second step of depositing copper, the application of the voltage was terminated when the copper concentration in the solution containing copper dissolved therein reached 18 g/L. An apparatus having a structure illustrated in FIG. 2 was used.

Example 2

Copper was produced as in Example 1, except that a solution having a V^(4.5+) concentration of 30 g/L and a copper ion concentration of 20 g/L was used as a solution containing an oxidant, a solution having a V^(3.5+) concentration of 30 g/L and a copper ion concentration of 20 g/L was used as a solution (A) containing the oxidant in a reduced state, and the voltage was 4.7 V in the second step of depositing copper. The temperature of the solutions was 28° C.

Electrolysis was performed for 15 hours in the second step of depositing copper, thereby depositing 1300 g of copper on the cathode. The copper had a purity of 99.9% or more. The electrodeposition efficiency was 91%.

The solution containing the oxidant and the solution (A) containing the oxidant in a reduced state were prepared by dissolving vanadyl sulfate (VOSO₄) in sulfuric acid to prepare a V⁴⁺-containing vanadium sulfate solution and electrolyzing the vanadium sulfate solution with an ion-exchange membrane. The copper ion concentration was adjusted by the addition of copper sulfate.

The term “V^(4.5+)” indicates that V⁵⁺ and V⁴⁺ are contained in equal proportions.

Similarly, the term “V^(3.5+)” indicates that V⁴⁺ and V³⁺ are contained in equal proportions.

REFERENCE SIGNS LIST

-   1 cathode -   2 anode -   3 rectifier -   4 separator -   5 solution containing copper dissolved therein -   6 solution containing oxidant in reduced state -   7 solution from which copper has been removed by deposition -   8 solution containing regenerated oxidant -   21 reservoir tank for solution containing oxidant -   22 dissolution tank -   221 copper-containing material -   23 reservoir tank for solution containing copper dissolved therein -   24 electrolytic bath -   241 cathode -   242 anode -   243 rectifier -   244 separator -   245 plating chamber -   246 oxidant regeneration tank -   25 reservoir tank for solution containing oxidant in reduced state 

1: A method for producing copper, comprising: a first step of dissolving copper by adding a copper-containing material to a solution containing an oxidant; and a second step of depositing copper on a surface of a cathode by bringing a solution (A) containing the oxidant in a reduced state into contact with a solution (B) containing the copper dissolved therein with a separator provided between the solution (A) and the solution (B), arranging an anode in the solution (A), arranging the cathode in the solution (B), and applying a voltage to both the electrodes, while the oxidant contained in the solution (A) is regenerated, wherein the oxidant has a standard electrode potential of 1.6 V or less. 2: The method for producing copper according to claim 1, wherein the oxidant is one or more selected from the group consisting of iron ions, manganese ions, vanadium ions, and chromium ions. 3: The method for producing copper according to claim 1, wherein after the second step of depositing copper, the solution (A) in which the anode is arranged is recovered, and the solution (A) is reused as the solution containing the oxidant in the first step. 4: The method for producing copper according to claim 1, wherein after the second step of depositing copper, the solution (B) in which the cathode is arranged is recovered, and the solution (B) is reused as the solution (A) in the second step. 5: The method for producing copper according to claim 1, wherein in the first step of dissolving copper, the copper-containing material is excessively added in such a manner that all the oxidant is in a reduced state. 6: The method for producing copper according to claim 1, wherein in the second step of depositing copper, the solution (B) containing copper dissolved therein has a copper concentration of 12 g/L or more. 7: An apparatus for producing copper used in the method for producing copper according to claim 1, comprising: a reservoir tank for a solution containing an oxidant; at least one dissolution tank; a reservoir tank for a solution containing copper dissolved therein; an electrolytic bath; and a reservoir tank for a solution containing the oxidant in a reduced state, wherein the electrolytic bath is partitioned with a separator into an oxidant regeneration chamber including an anode and a plating chamber including a cathode. 8: The apparatus for producing copper according to claim 7, wherein the at least one dissolution tank comprises a plurality of dissolution tanks. 